This invention pertains to a method and apparatus for securing elastic strands in disposable diapers where the strands impart an elasticized characteristic to the margins of the diapers and produce a sealing effect on the body so fluids will not leak out.
One existing method of securing elastic strands in diapers is described in U.S. Pat. No. 4,081,301 which issued on Mar. 28, 1978, and names K. B. Buell as the inventor. The entire disclosure of said patent is incorporated herein by reference.
The Buell patent teaches how to fabricate disposable diapers which are elasticized in the crotch and leg contacting region of the diaper so it fits snugly around the legs of an infant. A method suggested in this patent involves feeding a continuous moisture impervious sheet and a continuous stretched elastic strand toward a diaper assembly station. A quick setting glue is applied periodically over zones on the strand which are caused to adhere to the sheet in a region that will coincide with the crotch of the infant. In the process, a pad of an absorbent material is deposited on the backing sheet and it is overlayed with a nonwoven sheet whose edges are glued to what will become the edges of the finished diaper. When the web is cut into individual diapers, since the elastic strands are stretched where they extend from one diaper to another and are without adhesive in that region, the strands snap back into the diaper where they snarl or tangle undesirably. There are four unattached snapped back elastic strand ends each of which commonly exhibits a different bunched up and tangled configuration which by no means enhances the aesthetic quality of the diaper. Some diaper manufacturers avoid this problem by applying glue continuously to the stretched elastic strand such that when the glue on the strand sets in the diaper web and the web is cut into individual diapers the strand, being set, cannot snap back into the diaper. The problem with this is that the diaper is not only elasticized in the crotch region of an infant but also up into the waist region where elasticity is not needed nor desirable.
U.S. Pat. No. 4,353,762 issued in the name of F. J. Bouda on Oct. 12, 1982, teaches applying glue continuously to the rubber strand while the strand is stretched. But the parts of the strand extending beyond the crotch region in the diaper have the glue on them deactivated by a release agent which prevents the ends of the glue coated elastic strand from sticking to the diaper backing or facing sheets. However, it is apparent when the web is cut into individual diapers, the unattached ends of the strands which extend from diaper to diaper snap back into the diaper where they can bunch up at random.